FOCUS ON ROLL FORMING
A typical roll forming line . usually takes place at room temperature so that no additional energy is required for heating . For efficient operation , further processing steps ( such as the insertion of holes and embossing , the closing of closed profiles and cutting to the final profile length ) can be integrated into the system
Cutting to the final profile length means that no further cutting , which in turn causes scrap , is required when the profiles are assembled . Furthermore , as the fed strip usually has exactly the strip width required for the finished end product , there is no planned waste apart from the cutting slugs when the punched holes are inserted and any cutting waste ( e . g . for mitre cuts ). Planned waste is therefore only produced when a new coil is applied .
Planned scrap rates of significantly less than 1 % of the material used are therefore already within the realms of feasibility in roll-forming today . There are also robust approaches in roll forming for the second challenge , the minimisation of unplanned scrap . component parameters to be continuously monitored and a corresponding alarm to be triggered immediately if permissible tolerances are exceeded . This enables an immediate response to changes in the process , even before large quantities of rejects are produced .
Detecting profile straightness
However , there is one quality feature that has not yet been systematically monitored inline ; the straightness of the profiles in the
longitudinal direction . During the process , multidimensional stress states occur during roll forming which , in the worst case , lead to partial elongation of individual sections in the profile cross-section . This inhomogeneous longitudinal strain distribution leads to a curvature or twisting of the profile along the longitudinal axis , particularly for asymmetrical profiles .
Because of the clamping of the profile in the roll forming machine , these geometric defects are usually only recognisable after cutting . At this point in the production process ,
Minimising scrap
The illustration above shows a typical rollforming line .
From left to right , a coil is first unwound and the sheet is straightened . An optional processing station enables the end of one coil to be joined to the start of the new coil . This minimises the planned scrap when changing coils . Appropriate markings on the strip also allow the weld seam produced to be tracked as it passes through the system , so that the component with the transverse seam can be specifically ejected at the end . When using a coil that is several kilometres long , the scrap can be limited to just a few centimetres .
In the second processing station , the holes required for the profile are punched into the still flat belt . Camera systems at the outlet of the press continuously monitor the resulting punching pattern . If , for example , some of the holes are missing due to a broken punch , the machine can be stopped immediately without producing any more scrap . The quality of the weld seam created during the welding process can also be continuously monitored using camera systems in conjunction with image analysis .
The profile geometry , in turn , can be monitored using profile scanners , while the component length can be monitored by comparing the signal from a measuring wheel with the cut-off signal from the cut-to-length unit . This allows most of the quality-relevant
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